Air-bag arrangement and a method of inflating an air-bag

ABSTRACT

An air-bag arrangement provides protection for the occupant of a motor vehicle. The air-bag arrangement incorporates an airbag ( 50 ) formed by two layers ( 51, 52 ) interconnected to form a first set of chambers ( 53, 54, 55, 56, 57, 58 ), having a plurality of elongated substantially parallel chambers. A further fabric layer ( 61 ) is connected to one of the two layers ( 52 ) forming the main part of the inflatable element to define a second chamber set including two chambers ( 62, 63 ). The chambers are off-set from the adjacent chambers ( 54, 55, 56 ) defined by the first two layers ( 51, 52 ). Apertures ( 59, 60 ) provided in the layer ( 52 ) allow for the inflation of the second set of chambers ( 62, 63 ).

BACKGROUND OF THE INVENTION

The present invention relates to an air-bag arrangement, and moreparticularly relates to an air-bag arrangement adapted to provideprotection for an occupant of a motor vehicle in the event that a sideimpact or roll-over situation should occur.

It has been proposed previously to provide an air-bag arrangementincorporating an inflatable element initially stored in a recess orhousing which extends above the side door openings of a motor vehicle,the inflatable element being adapted to be inflated to occupy a positionbetween the occupant of the vehicle and the side doors of the vehicle.Thus the inflatable element can be considered to constitute aninflatable curtain.

Inflatable elements of this type are disclosed in GB 2,297,950 A. Thisspecification teaches an inflatable element formed of two adjacentsheets of fabric which are interconnected by seams to form a pluralityof cells. The configuration of the inflatable element is such that, asthe inflatable element becomes inflated, the cells take on asubstantially cylindrical configuration and a line of tension is createdso that the inflatable element is held substantially rigidly inposition.

It is important that the inflatable element should be deployed veryswiftly in response to a signal from a sensor indicating that a sideimpact, or a roll-over situation exists. It is also important,especially in a roll-over situation, that the inflatable element shouldbe maintained in the inflated state for a relatively long period oftime.

It is to be understood that, in a side impact or roll-over situation,the side window of a vehicle may break. Parts of a broken window maydamage an airbag which is located immediately adjacent that window, andthe air-bag may then lose gas and become deflated. This is clearlydisadvantageous.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved air-bag arrangementof the type discussed above.

According to this invention there is provided an air-bag arrangement foruse in a motor vehicle to provide protection for the occupant of themotor vehicle, the air-bag arrangement incorporating an air-bag adapted,on inflation, to be located adjacent an occupant of a vehicle, theair-bag comprising at least three super-imposed layers, each layer beingconnected to the or each adjacent layer to define a respective chamberset, at least one of the chamber sets incorporating a plurality ofchambers, the chambers of one chamber set being off-set relative to thechamber or chambers of another chamber set, means being provided tosupply gas to the chamber sets.

Preferably a first outer layer is connected to an intermediate layer todefine a plurality of chambers constituting said one chamber set, and asecond outer layer is connected to the intermediate layer to define atleast one chamber forming a second chamber set.

Conveniently the means to supply gas to the chamber sets comprises atleast a first gas duct in communication with one of the chamber sets

Preferably the means to supply gas additionally comprise a second gasduct to supply gas to a second chamber set.

Conveniently the means to supply gas to a chamber set comprise a regionof an intermediate layer which is adapted to permit a flow of gas from achamber set which is receiving gas to an adjacent chamber set which isto receive the gas.

In one embodiment the intermediate layer is provided, within saidregion, with an aperture.

In an alternative embodiment the intermediate layer is permeable to highpressure gas within said region.

In a further alternative embodiment the intermediate layer is adapted torupture or break within said region when subjected to a high pressure ofgas.

Preferably at least the outer layers are formed of fabric.

Conveniently the or each layer located between the outer layers is offabric.

Advantageously the air-bag is fabricated using a one-piece weavingtechnique.

In an alternative embodiment the or each layer intermediate the outerlayers is formed of foil.

Preferably the chambers of one chamber set are elongate and generallyparallel.

Conveniently the chambers of a second chamber set are elongate andparallel and are off-set from the chambers of the first chamber set.

Preferably the air-bag is provided with fixing means adapted to fix theair-bag to part of a motor vehicle extending above the side doors of thevehicle, the cells being located to extend generally transversely of anintended line of tension extending across part of the air-bag.

Conveniently the air-bag is provided with an extending strap adapted tobe connected to an anchoring point on the vehicle, said line of tensionextending from that anchoring point to one of said fixing means.

Advantageously the air-bag has a substantially rectangular portionaccommodating said chamber sets and an extension, the extensionconstituting a gas supply duct adapted to supply gas.

The invention also relates to a method of inflating an air-bag asdescribed above comprising the steps of initially inflating a firstchamber set, and subsequently inflating a second chamber set.

In one preferred embodiment of the invention the air-bag, when inflated,provides a uniform degree of protection across a selected area. In aconventional air-bag, which may be divided into a plurality of cells,formed from simply two layers of fabric, there are portions betweenadjacent cells where seams are located. If part of an occupant of avehicle strikes the region of the air-bag where a seam is located, theair-bag may provide only a minimum cushioning effect, or an insufficientcushioning effect. In preferred embodiments of the invention, where thechambers of the first chamber set are off-set relative to the chambersof the second chamber set, there is no region where there is simply aseam to be located between the occupant of the vehicle and the vehicleitself. Thus an improved protection is provided.

Another advantage of an air-bag in accordance with the present inventionis that if a window located adjacent the air-bag should break, withparts of the broken window damaging the air-bag, so that the air-bagloses gas, it will only be the set of chambers adjacent the window thatlose gas, and the air-bag will still have at least one further set ofchambers to provide a reasonable degree of protection for the occupantof the vehicle.

A further advantage obtained by use of a preferred embodiment of theinvention is that the layers of fabric utilised to form the air-bag,especially the intermediate layer or layers may have less coating thanis normally provided to ensure that the fabric is substantiallygas-tight, or even no coating at all. Because the inflatable elementcan, if designed appropriately, be subjected to a two-step inflationprocess, the coating may not be required. This can be advantageous sincethe coating can be relatively expensive.

A further advantage is that the chamber sets may be inflatedsequentially, thus prolonging the period of time during which theair-bag remains inflated.

A further advantage is that a first chamber set may have a relativelysmall volume, thus enabling the air-bag to be deployed swiftly. A secondchamber set, constituted by chambers located where protection isrequired (for example adjacent to the head of an occupant of thevehicle) may then be inflated—for example through a vent from the firstchamber set—so that the second chamber set is also inflated within arelatively short period of time.

In order that the invention may be more readily understood, and so thatfurther features thereof may be appreciated, the invention will now bedescribed, by way of example, with reference to the accompanyingdrawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a first outer fabric layer utilized in forming anair-bag, illustrating the pattern of seams used to secure the outerlayer to an intermediate layer.

FIG. 2 is a view of the intermediate layer, not showing any stitching,

FIG. 3 is a view corresponding to FIG. 1 illustrating an outer layerwhich is located on the opposite side of the intermediate layer to thelayer of FIG. 1, again showing the pattern of seams used to secure theouter layer to an intermediate layer,

FIG. 4 is a view showing the assembled air-bag, the seams of one of theouter layers being shown in solid, since they will be visible, and theseams of the other layer being shown in phantom, since they will not bevisible,

FIG. 5 is a sectional view taken on the line V—V of FIG. 4,

FIG. 6 is a plurality of sectional views taken on the lines shown inFIG. 5,

FIG. 7 is a perspective view of a modified embodiment of the invention,and

FIG. 8 is a sectional view of part of another modified embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIGS. 1, 2 and 3, an air-bag is fabricated fromthree layers of fabric. A first outer layer 1 of fabric is illustratedin FIG. 1. A second intermediate layer 2 of fabric is illustrated inFIG. 2, and a third outer layer 3 of fabric is illustrated in FIG. 3.The layers of fabric will be located with the two outer layers 1 and 3on opposite sides of the intermediate layer 2.

The three layers 1, 2 and 3 each have a substantially identical outershape. As can be seen most clearly in FIG. 2, each fabric layercomprises a central generally rectangular region 4. This region, as willbe described hereinafter, helps define inflatable cells. An extension 5extends from the top right-hand corner of the generally rectangularregion 4 of each fabric layer, as shown in FIG. 2. The extension 5 ofeach fabric layer, as will become clear hereinafter, helps constitute agas supply duct.

A plurality of projections 6 are provided extending across the upperpart of the rectangular region 4 and the extension 5. These projections6 form fixing lugs.

A further extension 7 in the form of a strap extends from the lowerleft-hand end of the rectangular region 4 of each fabric layer, as shownin FIG. 2. The extension 7, as will be described hereinafter, willconstitute a tensioning strap.

FIG. 1 illustrates the first outer layer 1 of fabric, and shows thepattern of seams that will be used to interconnect that layer of fabricand the intermediate layer 2 of fabric, as shown in FIG. 2. For thepurposes of explanation, it is to be understood that the first layer 1of fabric will be located behind the intermediate layer 2 of fabric, andequally the third layer 3 of fabric will be located in front of theintermediate layer 2 of fabric.

Looking initially at the rear-most layer 1 of fabric, it can be seenthat a seam 10 is provided which extends across the top of the layer 1of fabric, across the extension 5 that forms the gas supply duct and theseam continues, as seam 11, down the left-hand side of the rectangularregion 4. A seam 12 extends across the lower edge of the rectangularregion, and continues as seam 13 up the right-hand side of therectangular region 4. This seam then extends inwardly part way acrossthe rectangular region as seam 14 in alignment with the lower edge ofthe extension 5. A seam 15 is provided across the lower edge of theextension 5. A plurality of substantially vertical seams are provided,such as seams 16, 17, 18, 19, which extend upwardly from the lower seam12, but which terminate before the top seam 10.

In the described embodiment, the seams are formed by weaving togetherlayers of fabric using a one-piece weaving technique and, in thedescribed embodiment, in an area 20, which extends up from thelower-most seam 12, the layers are also woven together.

It can be understood that the configuration of seams, as describedabove, serves to define a gas flow duct 21 which extends adjacent theupper edge of the rectangular region 4, and a plurality of discretechambers 22, 23, 24, 25, 26 and 27, all of which are in gascommunication with the gas flow duct 21.

Considering now the outer layer 3 of fabric, as shown in FIG. 3, it canbe seen that this layer 3 of fabric is also provided with seams 10 to15, as described above. This layer 3 of fabric is provided with aplurality of seams 28, 29, 30 which extend upwardly from the lower-mostseam 12 towards the top seam 10. Again the seams are formed by weavingthe layers of fabric together and, again, there is an area 20 where thefabric of the layer 3 is woven together with the fabric of theintermediate layer, and also, as will be apparent, with the fabric ofthe first outer layer 1.

It is to be observed that the seams 28, 29 and 30 of the third outerlayer of fabric 3 are laterally off-set from the seams 16, 17, 18 and 19of the first outer layer 1 of fabric.

The outer layer 3 of fabric together with the intermediate layer 2 offabric form a gas flow duct 31 which extends in alignment with the gassupply duct 5 across the top of the rectangular area 4, the gas flowduct 31 communicating with discrete chambers 32, 33, 34, 35 and 36defined by the seams 28, 29, 30.

At least some of the seams may be mechanically weak, and thus areadapted to rupture. The intermediate layer may be provided with one ormore regions 40 adapted to permit a flow of gas when subjected to a veryhigh pressure of gas. The region 40 may be a region which is permeableto high pressure gas or may be a region which ruptures or breaks whensubjected to high pressure. The region 40 may, in alternative designs,be replaced by permeable or rupturable seams to provide the same effect,or the region 40 may simply be provided with an aperture. The region 40may be located at any convenient position, and may thus separate the twogas flow ducts, or may separate two adjacent chambers.

It is to be appreciated, therefore, that the three layers 1, 2 and 3 offabric may be woven simultaneously and may be interconnected with thedescribed seam patterns using a one-piece weaving technique to producean air-bag which effectively comprises a first plurality of chambersconstituting a first chamber set defined between one outer layer offabric, and an intermediate layer of fabric, and a second discreteplurality of chambers forming a second chamber set defined between asecond outer layer of fabric and the said intermediate layer of fabric.

The chambers are configured to extend generally transversely to anintended tension line, shown as the line T in FIG. 4, which extends fromthe strap 7 to one of the fixing lugs 6 provided on the extension 5. Ina modified arrangement a further strap may be provided at the right-handlower corner of the rectangular region 4, and the line of tension mayextend along this strap and also along the strap 7.

It is intended that the air-bag will be mounted in a motor vehicle withthe lugs 6 being connected to points located above the door opening atthe side of the vehicle strap formed by the extensions, with the strapextending to an anchoring point present, for example, on the “A”-Post ofthe vehicle.

It is envisaged that the air-bag described above will be utilized inconnection with a gas generator assembly adapted to supply gasseparately to the two discrete sets of chambers.

FIG. 5 illustrates the situation that exists when the air-bag has beeninflated and, as can be seen from FIG. 6, the extension piece 5 isactually configured to define two gas supply ducts, namely a first gassupply duct 41, that communicates with the chambers 22, 23, 24, 25, 26,27, and a second gas supply duct 42 that communicates with the chambers32, 33, 34, 35, 36.

It is envisaged that gas may be supplied through one duct, such as theduct 41, in order rapidly to inflate the chambers associated with thatduct, thus deploying the air-bag swiftly to its intended operativeposition. In many side impact situations it is important that an air-bagshould be deployed as swiftly as possible to provide protection for theoccupant of the vehicle. The chambers 22, 23, 24, 25, 26, 27 will thusbecome inflated reducing the length of the portion of the air-bag thatextends between the anchoring point to which the strap 7 is connectedand one of the lugs 6, such as a lug on the extension piece 5, creatingthe line of tension T. The axes of the cells extend transversely to theline of tension. The chambers 22, 23, 24, 25, 26, 27 may be designed tohave a relatively small volume so that they may inflate relativelyquickly, thus deploying the air-bag rapidly.

It is envisaged that, subsequently, gas may be supplied through the gassupply duct 42 to the chambers 32, 33, 34, 35, 36. These chambers, asthey inflate, enhance the tensioning effect along the line of tension T.The effect of this will be to prolong the period of time during whichthe inflatable element is actually inflated. This is a desirableproperty of an inflatable element of this type, especially during aroll-over accident situation.

It is to be noted that because the seams interconnecting the first outerlayer 1 of fabric and the intermediate layer 2 to form the first set ofchambers are off-set from the seams joining the second outer layer 3 offabric to the intermediate layer 2 to form the second set of chambers,the resultant chambers are off-set and substantially overlap each other,as can be seen most clearly from the sectional view of FIG. 5. Thus,regardless of which set of chambers is inflated, the air-bag will, inthe areas where the cells are located, provide at least some degree ofprotection for an occupant of the vehicle. Of course, the degree ofprotection that is provided is optimum when both sets of chambers areinflated, since then there is no part of the region of the air-bagcovered by the overlapping chambers that is not inflated. This is incontrast with the risk, if there is only a single set of chambers, thatpart of the occupant will hit the air-bag precisely where there is aseam between adjacent chambers, with the consequence that the air-bagdoes not provide adequate protection. Also, by the provision of two setsof chambers, and by the inflation of those chambers at different times,a satisfactory degree of protection may be provided over a relativelylong period of time.

It is to be appreciated that if the air-bag, when inflated, is locatedadjacent a window which breaks, and if part of the broken window shoulddamage the fabric of the air-bag that lies adjacent the window, only oneset of chambers will be damaged. Thus, whilst that set of chambers maybegin to deflate, the other set of chambers will still remain inflatedto provide protection for the occupant of the vehicle.

It is possible that a sensor may be utilized which is adapted to sensespecific parameters concerning an accident situation, and the time atwhich the two gas generators are activated may be dependent upon thesensed parameters.

The presence of the region 40 in the intermediate layer 5 is such thatif a particularly high pressure of gas exists in one gas flow duct, andthe associated chambers, (such as the gas flow duct 21 and theassociated chambers 22, 23, 24, 25, 26 and 27) gas from that gas flowduct, or the associated chambers, may transfer to the other gas flowduct and assist in the inflation of the other set of chambers.

It is to be appreciated that the design of each of the outer layers 1, 3of fabric may be modified independently to produce a range of productsadapted for use with a range of motor vehicles.

Whilst, in the described embodiment, all three layers of fabric have thesame configuration, it is to be appreciated that in modifiedembodiments, the three layers of fabric may have differentconfigurations. Thus, it is conceivable that in one embodiment of theinvention, one outer layer and the intermediate layer have the sameconfiguration, and the second outer layer has a different configuration,being rather smaller than the first outer layer and the intermediatelayer. This may facilitate the provision of relatively small cells, or asingle cell, or a small number of cells, on one side of the intermediatelayer which can be inflated very rapidly indeed, since the cell or cellswill only contain a very small quantity of gas when fully inflated, thusenabling the airbag to be deployed to the operative position withextreme rapidity.

Thus, as shown in FIG. 7, an air-bag 50 is shown in the inflated state.The air-bag 50 comprises a first outer layer 51 and an intermediatelayer 52 which are of the same configuration and which are securedtogether by appropriate seams to define chambers, identified as chambers53 to 58 which correspond with the chambers 22 to 27 formed between theouter layer 1, as shown in FIG. 1, and the associated intermediate layer2, as shown in FIG. 2.

The intermediate layer of fabric 52 is provided with an aperture 59 inthe wall of cell 55. A further aperture 60 is formed in the wall of cell54.

A rectangular layer of fabric 61 is secured to the exterior of theintermediate layer 52 partially overlapping the chambers 54, 55 and 56.Seams are provided so that the layer 61 forms two chambers 62, 63. Thechamber 62 is in communication with the aperture 60, and the chamber 63is in communication with the aperture 59. It can be seen that oninflation of the airbag 50 as shown in FIG. 7, initially the chambers 53to 58 will become inflated. As the chambers 54 and 55 become inflated,gas will flow through the apertures 59 and 60 into the chambers 62 and63. In the embodiment a two-step gas generator may be used to provideinflating gas over a relatively long period of time.

It is to be appreciated that if the seams in any embodiment of theinvention are relatively weak, energy may be absorbed, by the tearing ofthose seams, should the head of an occupant of a vehicle impact with theair-bag when it is inflated.

Whilst the invention has been described with reference to preferredembodiments, it is to be appreciated that many modifications may beeffected. For example, whilst the invention has been described withreference to an embodiment in which the gas supply duct is provided atthe top of the inflatable element, the gas supply duct may be providedat the lower edge of the inflatable element. The air-bag may be designedto extend over both a front and a rear door. Thus the air-bag may extendfrom a point on the A-Post to a point on the C-Post with no extensionpieces or straps.

Again, whilst in the preferred embodiment of the invention, two gasducts are provided, one supplying the first set of chambers and theother supplying the second set of chambers, it is to be appreciated thata single gas duct may be provided which inflates both sets of chamberssimultaneously. Alternatively, a single gas supply duct may inflate oneset of chambers and gas may then flow, for example through a permeablepart of the intermediate layer, from part of that gas duct, or one ofthe inflated chambers into the second set of chambers.

Whilst, in the described embodiment, the second set of chamberscomprises a broadly equivalent number of chambers to that of the firstset of chambers, in modified embodiments of the invention there may onlybe a single chamber in the second set of chambers, or the second set ofchambers may be constituted by a small number of chambers, or a numberof small chambers.

Again, whilst the invention has been described with reference to anembodiment in which three layers of fabric are utilized to form theair-bag, in a modified embodiment of the invention of the air-bag couldbe formed from two layers of fabric forming an outer layer and anintermediate layer, and the other outer layer could be formed of a foil.The foil may be relatively thin layer formed, for example, of anappropriate plastics material. In an embodiment of this type of aplurality of layers of foil may be provided, thus providing three ormore sets of chambers, with the chambers being mutual off-set. Theseams, where a foil layer is used, may be ordinary stitching, or gluedor welded seams may be used.

FIG. 8 is a sectional view illustrating a further modified embodiment ofthe invention, the sectional view being equivalent to the left-hand partof FIG. 5. It can be seen that in this embodiment of the invention,there are two outer layers 70, 71, and two intermediate layers 72, 73.Thus, three chamber sets are formed, one chamber set being formedbetween the outer layer 70 and intermediate layer 72, a further chamberset being formed between the intermediate layer 72 and intermediatelayer 73 and a third chamber set being formed between the intermediatelayer 73 and the outer layer 71. The chambers formed by each outer layerare in alignment with each other, but the chambers formed between thetwo intermediate layers are off-set from these aligned chambers. It isto be appreciated that even more intermediate layers may be utilized,with the result that even more chamber sets are defined.

In the present specification “comprise” means “includes or consists of”and “comprising” means “including or consisting of”.

The features disclosed in the foregoing description, or the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the disclosed function, or amethod or process for attaining the disclosed result, as appropriate,may, separately, or in any combination of such features, be utilized forrealizing the invention in diverse forms thereof.

1. An air-bag arrangement for use in a motor vehicle to provideprotection for an occupant of the motor vehicle, the air-bag arrangementincorporating an air-bag adapted, on inflation, to be located adjacentan occupant of a vehicle, the air-bag comprising at least threesuper-imposed layers including a first outer layer, an intermediatelayer and a second outer layer, each layer being formed of fabric andconnected to the or each adjacent layer to define a respective chamberset where the intermediate layer is attached to both the first andsecond layers at locations where the first and second layers areconnected, at least one of the chamber sets incorporating a plurality ofchambers, the chambers of one chamber set being off-set relative to thechamber or chambers of another chamber set so as to substantiallyoverlap the chamber or chambers of another chamber set and means beingprovided to supply gas to the chamber sets wherein the air-bag isfabricated using a one-piece weaving technique, and wherein the air-baghas an extension, the extension constituting a gas supply duct adaptedto supply gas to at least one of the chamber sets.
 2. An arrangementaccording to claim 1 wherein the first outer layer is connected to theintermediate layer to define a plurality of chambers constituting saidone chamber set, and the second outer layer is connected to theintermediate layer to define at least one chamber forming a secondchamber set.
 3. An arrangement according to claim 1 wherein the gassupply duct is adapted to supply gas to one of the chamber sets.
 4. Anarrangement according to claim 3 wherein the extension additionallycomprises a further gas duct to supply gas to a second chamber set. 5.An arrangement according to claim 3 wherein the means to supply gas to achamber set comprise a region of the intermediate layer which is adaptedto permit a flow of gas from a chamber set which is receiving gas to anadjacent chamber set which is to receive the gas.
 6. An air-bagaccording to claim 5 wherein the intermediate layer is provided, withinsaid region, with an aperture.
 7. An air-bag according to claim 5wherein the intermediate layer is permeable to high pressure gas withinsaid region.
 8. An arrangement according to claim 5 wherein theintermediate layer is adapted to rupture or break within said regionwhen subjected to a high pressure of gas.
 9. An arrangement according toclaim 1 wherein the chambers of one chamber set are elongate andgenerally parallel.
 10. An arrangement according to claim 9 wherein thechambers of a second chamber set are elongate and parallel and areoff-set from the chambers of the first chamber set.
 11. An arrangementaccording to claim 9 in which the air-bag is provided with fixing meansadapted to fix the air-bag to part of a motor vehicle extending abovethe side doors of the vehicle, the chambers being located to extendgenerally transversely of an intended line of tension extending acrosspart of the air-bag.
 12. An arrangement according to claim 11, whereinthe air-bag is provided with an extending strap adapted to be connectedto an anchoring point on the vehicle, said line of tension extendingfrom that anchoring point to one of said fixing means.
 13. Anarrangement according to claim 1 wherein the air-bag has a substantiallyrectangular portion accommodating said chamber sets and the extension.14. An arrangement according to claim 1 wherein each of the said layersof fabric are of substantially identical shape and size.
 15. A method ofinflating an air-bag according to claim 1 comprising the steps ofinitially inflating a first chamber set, and subsequently inflating asecond chamber set.